The YouTube video shows a simple method to try and find out if the RF FET is fake or genuine. Many EBay sellers are selling fake RF FETS that are actually other very cheap or reject packages. It is not easy to determine if a FET is genuine. Sometimes the poor quality of the printing and package are a clue. However a simple DC test and using the data sheet will tell you more. The final test will always be the actual amplifier performance such as gain, linearity, frequency response, and power output.